reverse flow on a sump?

[ABATTLEDONKEY]

hello,
i would like to add a sump but i have a problem. the tank i have now (a 55 gal) was origionally a freshwater tank. the stand i have it in now was built my my friend and i to custom fit this tank. being as how it was built for a fresh water tank we never thought twice about setting up a sump/refugium. as a result the tank only sits about 1 1/2 feet off the ground with no access under teh display tank. there are some very large cabinets on either side that are being used for various different things. so in setting up a sump i have very little to no room, or a very long way to get there. the tank is also glass and so drilling isnt an option for me and overflow boxes are a thing id like to avoid. my idea was to go against the flow and put the sump above the display tank rather than below it. i would do this by having the water pumped up to the sump and gravoty fed back down to the display tank. im new to the salt water scene and even greener to the sump scene. im not sure what possible risks might be involved in this setup and would not like to try an experiment on my already money draining tank. any help or insight would be greatly appreciated. thanks
-Paul

 

[seapug]

That's called an upstream refugium. It'll work, but just like the reverse of a sump below the tank, you have to build it correctly so in the event of a power outage it doesn't siphon back to the tank and overflow it. A google search will probably yield more info.

 

[ReefWreak]

Lots of people would prefer to have an upstream refugium, as it means that pods and other things that breed in the refugium will naturally fall down into the tank, feeding it, without having to go through a pump and "theoretically" get chopped up by the blades.

The way to prevent an overflow from happening from the top tank is to have an overflow, drilled or HOB/weir going down to the bottom tank. I would also HIGHLY suggest drilling the midpoint of a HOB/wier, placing a small airline nipple on it, and running a aqualifter pump on it to ALWAYS keep it primed, so it won't break siphon and flood the top tank. The Aqualifter is a good pump for that job because it'll suck up air and/or water with ease.

 

[ABATTLEDONKEY]

thanks for the help guys.

for an overflow i was just thinking about cutting a sizable hole straight through the tank slightly below the top so the more the tank fills, the more it would fall back down. it would keep a constant water level and would eliminate the risk of siphoning back down in the event of a power outage. as long as the drain plug can accommodate a larger water flow than the pump can supply i dont think that will be an issue. can you see and cons?

i was also interested in knowing what kind of flow rate i should have. the tank im hooking it up to is a 55 gallon. i only have 2 fish in it, a blue hippo tang(i know i know, its very small right now and i plan on trading it in when it gets bigger.... or possibly convincing my wife to let me get a bigger tank ), and a flame angel. i have no corals. im not going to try and use this sump as a way to increase flow in the main tank but im not sure how much flow i should have in the sump/refugium it self. any help is appreciated. thanks
-Paul